Introduction to Endocrinology Flashcards
What are the major endocrine glands?
Hypothalamus Pituitary gland Thyroid, adrenal cortex, gonads Pancreas Parathyroid glands
What do each of the major endocrine gland secrete?
Hypothalamus - Releasing & inhibiting hormones
Pituitary gland -
Anterior lobe - trophic hormones Posterior lobe – oxytocin & vasopressin (ADH)
Thyroid gland - Thyroxine, tri-iodothyronine
Adrenal gland -
Cortex: Cortisol, aldosterone
Medulla: Adrenaline/noradrenaline
Gonads - Oestrogens, androgens, progestogens
Pancreas - Insulin, glucagon
Parathyroid gland - Parathyroid hormone
Others - Kidney (Vit. D, EPO), CVS (ANP, endothelins), pineal gland (melatonin), thymus gland (thymic hormones), bone (phosphate), adipose tissue (leptin)
What are the different signalling mechanisms in the endocrine system?
Endocrine- Hormones released by an endocrine cell into the general circulation and acting on distant target sites
Paracrine- Hormones released by an endocrine cell which act locally on adjacent cells
Autocrine- Hormones released by a cell which act back on the same cell (sometimes also seen in diseases like cancer)
Intracrine- Conversion of an inactive hormone that acts within that cell (so a steroid hormone that acts on a steroid receptor acting within the cell)
What are the general functions of hormones?
Reproduction , growth and development- sex steroids, thyroid hormones, prolactin, growth hormone
Maintenance of internal environment- aldosterone, parathyroid hormone, vitamin D
Energy production, utilisation and storage- insulin, glucagon, thyroid hormones, cortisol, growth hormone
What are the chemical classifications of hormones (e+)?
Protein/peptide hormones: Hypothalamic hormones Pituitary hormones Insulin PTH Calcitonin Steroid hormones (e.g. hormones derived from cholesterol): Cortisol Aldosterone Oestrogens Androgens Progestogens Vitamin D Amino acid derivatives (tyrosine/tryptophan derivatives)(also classed within peptide family): Adrenalin Noradrenaline (tyrosine) Melatonin (tryptophan) Fatty acid derivatives: Prostaglandins Thromboxanes Prostacyclin
What is the chemical nature of hormones and their transport?
Proteins and peptide hormones have a half life in circulation of minutes and are transported mainly unbound Tyrosine derivatives (catecholamines) have a half life of seconds while thyroid hormones have a half life of hours and travel bound to plasma proteins Cholesterol derivatives (all steroids) have a half life of hours-days and travel bound to plasma proteins
What is the hypothalamic-pituitary axis and what does it do?
Hypothalamic–pituitary axis and the hormones secreted by the anterior and posterior lobes of the pituitary gland
Magnocellular neurones in the hypothalamus synthesise and release posterior pituitary hormones
Other neurosecretory cells in the hypothalamus release their hormones into the portal capillaries in which they are transported directly to endocrine cells of the anterior pituitary gland
How do hypothalamic secretions control the anterior pituitary secretions?
The hormones released from the hypothalamus that act on the anterior pituitary and what hormones are subsequently stimulated or inhibited
Examples are:
CRH stimulates ACTH
TRH stimulates TSH while somatostatin inhibits it
GnRH stimulates LH and FSH
Dopamine inhibits prolactin
GHRH stimulates GH while GHIH (somatostatin) inhibits it
What are the general disorders of the endocrine system?
Excess or deficiency
Impaired synthesis
Transport and metabolism of hormones
Resistance to hormone action
How can the control of cortisol or lack thereof lead to disorders?
Cortisol is regulated through the hypothalamic pituitary axis
The hypothalamus secretes CRH which goes on to act on the anterior pituitary and that releases ACCTH which act on the adrenal cortex to release cortisol
Cortisol has a number of effects:
Gluconeogenesis
Protein mobilisation
Fat mobilisation
Anti-inflammatory effects
A deficiency can lead to Addison’s disease
An excess of cortisol can lead to a disorder called Cushing’s disease
